Author Topic: Replaced piston/cylinder now won't fire  (Read 1080 times)

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Offline Adirondackstihl

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Re: Replaced piston/cylinder now won't fire
« Reply #20 on: October 20, 2013, 08:49:36 pm »
So I'll need to remove the handle/tank to get to the crank seams right? 
No. But you will need to remove the flywheel and clutch t actually see any bubbling from the seals. Removing the flywheel....no problem. Removing the clutch may cause you some difficultly without the $8 removal socket.

Where are you from? Ship the saw to me if you want......I'll get it running. Or perhaps someone lives close to you that could lend a hand?

Offline sharkey

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Re: Replaced piston/cylinder now won't fire
« Reply #21 on: October 21, 2013, 12:40:25 am »
So I'll need to remove the handle/tank to get to the crank seams right? 
The crank seals are behind the clutch and behind the flywheel.  Use a piece of rope down through the spark plug hole to lock down the crank so you can turn the nuts.  Remove the clutch by reverse thread meaning it turns clockwise to loosen.  On the flywheel side, loosen the flywheel nut but dont take it all the way off the crank.  Use a soft hammer and tap the nut at the top of the crank threads (to protect them) and off pops the flywheel.         

Offline Spike60

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Re: Replaced piston/cylinder now won't fire
« Reply #22 on: October 21, 2013, 07:08:51 am »
Even with most of the carb/intake/seal issues that are being discussed, the saw should fire on a squirt of fuel if it has compression and spark.

Even if there is a visual spark, the coil could still be bad. It could be weak on reserve voltage or firing out of time.  Often this can be detected by weak pop that sounds like the deco is locked open.
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Offline KilliansRedLeo

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Re: Replaced piston/cylinder now won't fire
« Reply #23 on: October 24, 2013, 05:59:16 am »
Spike60 is correct, are you sure the coil is grounded properly?
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Offline jmester

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Re: Replaced piston/cylinder now won't fire
« Reply #24 on: October 24, 2013, 09:10:44 pm »
Is the plug getting any fuel. Spark is great, but no fuel means not going to run.
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Offline wbhburn

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Re: Replaced piston/cylinder now won't fire
« Reply #25 on: October 26, 2013, 01:39:49 pm »
I removed everything required to do the vacuum test but I did not have enough hands to hold the saw, reach the impulse tube, pump in the air from the syringe and check for leaks at the same time. However, I did a very close inspection and saw no areas around the case gasket that could be leaking. I "orally" checked the I manifold and determined it held pressure (no leaks). Reassembled and still no fire. Spark looks good and strong. Questions...

Even if there is a pin hole leak somewhere in the case wouldn't it at least fire?
How can I "prime the thing" just to get it to fire once?
Do I add a bit of gas in the carb throat or in the plug hole? I just want to hear it fire once :-)
I'm willing to up-grade to the new carb and manifold Cut4fun suggested. Where to purchase?
If it was running before could the old carb/manifold really be the problem?

Offline 660magnum

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Re: Replaced piston/cylinder now won't fire
« Reply #26 on: October 26, 2013, 02:14:16 pm »
A two stroke engine with an open seal (or no crankcase vacuum/pressure) If primed in the spark plug hole, should "POP" every time you pull it over but never actually start and run. The same goes for a reed valve two stroke with a bad reed or a engine with a closed carb butterfly.
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Offline wbhburn

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Re: Replaced piston/cylinder now won't fire
« Reply #27 on: October 26, 2013, 02:24:49 pm »
No "Pop"

I have a VOM. Can I use it to check coil output?

Offline wbhburn

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Re: Replaced piston/cylinder now won't fire
« Reply #28 on: October 26, 2013, 02:27:02 pm »
Oh, and how about timing?
Could these things have changed after piston/cylinder replacement?

Offline wbhburn

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Re: Replaced piston/cylinder now won't fire
« Reply #29 on: October 26, 2013, 02:34:18 pm »
Before I forget - thanks to all for the attention

So, now that I think about it, here's the logic as I see it. PLEASE correct me if I'm wrong....

a) Even with a vacuum leak I should get some bang or pop with a bit of fuel manually applied.
b) In the absence of that indication, one could assume an electrical problem
c) My focus should be on electrical and all the other possibilities would be secondary until I get some fire after prime

As I asked before, how to trouble shoot electrical (and please don't assume I know ANYTHING)? Step by step if you have the patience. Again, I do know how to use my Fluke VOM, will that help?

 

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